needle in the haystack, maybe yes, maybe no, but the good thing is that we're actually in an urban environment and there's a lot of buildings around and other materials that will stop some of this evidence as it crawls across the pavement and it will be found. the agents will go in and start conducting a crime scene investigation to find even the most minute pieces of evidence and what we call bag and tag and send to the laboratory. in the laboratory, the forensic scientists, examiners, will look at these pieces of debris and then start making conclusions as to what the device consisted of. >> how do you-- i understand how you could piece together what was the bomb made of. how did it work, how was it detonated and so on. but how-- we're told in the pan am 103 bombing which you helped investigate, that it was a thumbnail sized piece of evidence that led to the identity of the bomber. i mean, how can that be? how can you get to the identity from the remnants of the bomber? >> well, sometimes in pan am 103, the fragment of the circuit board that was the timer that detonated the device, is so gen